1. Field of the Invention
The present disclosure relates to a mask for forming a black matrix for a display device including a data line having a bending structure with respect to a central portion of a pixel region.
2. Discussion of the Related Art
With rapid development of information technologies, display devices for displaying a large amount of information have been promptly developed. More particularly, flat panel display (FPD) devices having a thin profile, light weight and low power consumption such as organic electroluminescent display (OLED) devices and liquid crystal display (LCD) devices have been actively pursued and have been replacing the cathode ray tubes (CRTs).
Among the various types of FPD devices, liquid crystal display (LCD) devices have been widely used as monitors for notebook computers and desktop computers because of their excellent contrast ratio, low power consumption and superiority in displaying moving images. The LCD device uses optical anisotropy and polarization properties of liquid crystal molecules. The liquid crystal molecules have a definite alignment direction as a result of their thin and long shapes. The alignment direction of the liquid crystal molecules can be controlled by applying an electric field across the liquid crystal molecules.
Generally, an LCD device includes a liquid crystal panel, which comprises a first substrate having an array layer for driving liquid crystal molecules, a second substrate having a color filter layer for producing colors, and a liquid crystal layer therebetween. The arrangement of the liquid crystal molecules varies depending on an electric field, and transmittance of light passing through the liquid crystal panel is controlled.
The LCD device further includes a backlight under the liquid crystal panel. Light from the backlight passes through the liquid crystal panel, and a color image is displayed due to the color filter layer.
The LCD device may be manufactured through a substrate-fabricating process for forming elements on first and second substrates, a cell process for completing a liquid crystal panel, and a module process for combining the liquid crystal panel and a backlight.
The substrate-fabricating process includes a thin film deposition process, a photo-lithography process, an etching process, and so on, which are repeated several times, to form pixel electrodes and thin film transistors.
The photo-lithography process forms a photoresist pattern by applying photoresist to a substrate having a thin film, exposing the photoresist to light through a mask, and developing the photoresist.
An exposure apparatus for exposing the photoresist to light may be classified into a projection type and a proximate type. The projection type has a merit of a high resolution of the photoresist pattern and has demerits of high costs and a slow exposure speed as compared with the proximate type. Therefore, recently, the proximate type exposure apparatus has been widely used.
FIG. 1 is a plan view of illustrating a mask for forming a black matrix having a plurality of patterns according to the related art, and FIG. 2 is a plan view of illustrating a light-transmitting portion of the mask and a photoresist pattern for comparison.
In FIG. 1, a mask 10 for forming a black matrix, which is formed on an upper substrate (not shown) opposite to a lower substrate having a pixel electrode and a thin film transistor, includes an edge frame 11 disposed along its edges and a base plate 21 disposed on the edge frame 11. The base plate 21 includes a light-transmitting portion 23 and a light-blocking portion 25. The light-transmitting portion 23 has a size corresponding to a photoresist pattern for the black matrix. The light-blocking portion 25 is disposed between adjacent light-transmitting portions 23 and surrounds each light-transmitting portion 23.
As shown in FIG. 2, the photoresist pattern 30 for the black matrix, which is formed using the mask 10, is larger than the light-transmitting portion 23 of the mask 10. More particularly, the light-transmitting portion 23 of the mask 10 has a first width w1, and the photoresist pattern 30 formed on a substrate (not shown) has a second width w2 wider than the first width w1. The difference between the first width w1 and the second width w2 is referred to as a critical dimension bias.
Recently, as the display device has high definition and high resolution, it is important to form fine photoresist patterns, and the critical dimension of the minimum photoresist pattern is about 7 micrometers due to a decrease in a line width and a limitation in the photo-lithography process.
Thus, if the second width w2 of the photoresist pattern is less than 7 micrometers, the light-transmitting portion 23 can not be formed in the mask 10 considering the critical dimension bias. That is, it is not possible to form the fine photoresist pattern when the second width w2 of the photoresist pattern is less than 7 micrometers.